Lens and light emitting module for surface illumination

ABSTRACT

A light emitting module includes a circuit board, light emitting elements disposed on the circuit board, each light emitting element including light emitting diode chips and a wavelength conversion layer coated on the light emitting diode chips, and a lens disposed on the light emitting elements and configured to diffuse light emitted from the light emitting elements. The lens includes a concave part having a light incident surface and an upper surface through which the light incident on the lens is emitted, and at least one of the light incident surface and the upper surface includes sections disposed at least 15° from a central axis and sequentially connected in a first direction.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from and the benefit of Korean PatentApplication 10-2013-0101191, filed on Aug. 26, 2013, which is herebyincorporated by reference for all purposes as if fully set forth herein.

BACKGROUND

Field

Exemplary embodiments of the present invention relate to a lightemitting module, and more particularly, to a lens for surfaceillumination and a light emitting module for surface illuminationincluding the same.

Discussion of the Background

A light emitting module for backlighting a liquid crystal display or alight emitting module for surface illumination used in a surfaceillumination apparatus may include light emitting elements mounted on acircuit board and a lens for diffusing light emitted from the lightemitting elements at a wide angle. Light may be uniformly irradiatedover a wide area with a smaller number of light emitting elements byuniformly diffusing the light emitted from the light emitting elementsusing the lens.

FIGS. 1A and 1B are schematic cross-sectional view and perspective viewfor describing a light emitting module and a lens according to therelated art.

Referring to FIGS. 1A and 1B, the light emitting module includes acircuit board 100, a light emitting element 200, and a lens 300. Thecircuit board 100 may be a printed circuit board provided with a circuitfor supplying power to the light emitting element 200.

The light emitting element 200 may include a light emitting diode chip210, a molding part 230 covering the light emitting diode chip 210, anda package substrate 250. The molding part 230 includes a phosphorconfigured to convert a wavelength of light emitted from the lightemitting diode chip 210, and which may have a lens shape. The packagesubstrate 250 may have a recess for mounting the light emitting diodechip 210. The light emitting element 200 is electrically connected tothe circuit board 100.

Meanwhile, the lens 300 may include a lower surface 310 and an uppersurface 350, and may further include a flange 370 and leg parts 390. Theleg parts 390 are attached on the circuit board 100 so that the lens 300is disposed over the light emitting element 200. As illustrated in FIG.1B, the leg parts 390 are may be configured as a group of three anddisposed at regular triangular apexes.

The lens 300 includes a light incident surface 330 on which light isincident from the light emitting element 200 and a light emittingsurface 350 from which the incident light is emitted. The light incidentsurface 330 is an inner surface of a concave part 320, which may beshell-shaped, which is disposed on the lower surface 310 of the lens300. The concave part 320 is disposed on the light emitting element 200and thus the light emitted from the light emitting element 200 isincident into the lens 300 through the light incident surface 330. Thelight emitting surface 350 emits the light incident into the lens 300 ata wide orientation angle.

The light emitting module according to the related art diffuses thelight emitted from the light emitting element 200 through the lens 300to implement uniform light over a wide area. However, the light emittingelement 200 mounted on the circuit board 100 may adopt the packagesubstrate 250, and therefore a size of the light emitting element 200may be relatively large. Therefore, an inlet and a height of the concavepart 320 for forming the light incident surface 330 of the lens 300 maybe relatively large, and as a result, it may be difficult to slim thelens 300. In addition, the beam angle spread of light emitted from thelight emitting element 200 may be relatively narrow, and therefore itmay be difficult to diffuse light through the lens 300.

Further, the light emitting element 200 is disposed under the lowersurface 310 of the lens 300 and therefore some of the light emitted fromthe light emitting element 200 may not be incident into the lens 300 andmay be lost below the lower surface 310 of the lens 300.

SUMMARY

Exemplary embodiments of the present invention provide a technology forslimming a lens for a surface light source and a light emitting module.

Exemplary embodiments of the present invention also provide a lens and alight emitting module capable of reducing a loss of light emitted from alight emitting element.

Exemplary embodiments of the present invention also provide a lightemitting module capable of providing light having uniform colordistribution and luminous intensity over a wide area by adopting a lightemitting element suitable for a surface light source.

Additional features of the invention will be set forth in thedescription which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention.

An exemplary embodiment of the present invention discloses a lightemitting module including: a circuit board; light emitting elementsmounted on the circuit board; and a lens coupled with the circuit boardand diffusing light emitted from the light emitting elements. The lensincludes a concave part defining a light incident surface on which lightis incident and the light emitting element is substantially disposedwithin a concave part of the lens. Since the light emitting elements aredisposed within the concave part, most of the light emitted from thelight emitting elements may be incident into the lens to reduce a lossof light below a lower surface of the lens.

The light emitting element is a chip level light emitting element anddiffers from the light emitting diode package including a package mainbody according to the related art. That is, the light emitting elementdoes not include a mounting member for mounting a light emitting diodechip and the circuit board is used as the mounting member for mountingthe light emitting diode chip.

The chip level light emitting element includes the light emitting diodechip and a wavelength conversion layer coated on the light emittingdiode chip. The wavelength conversion layer may cover an upper surfaceand side surfaces of the light emitting diode chip. In particular, thelight emitting diode chip may be a flip chip type light emitting diodechip flip-bonded to the circuit board. The flip chip type light emittingdiode chip may be directly mounted on the circuit board to more reduce asize of the light emitting element than that of the light emittingelement according to the related art using the package substrate,thereby slimming the light emitting module. Further, since the size ofthe light emitting element is small, a size of the concave part of thelens may be reduced and an overall height of the lens may be reduced.

A width of an inlet of the concave part of the lens may be less thanthree times a width of the light emitting element. The width of theinlet of the concave part may be set to be less than three times thewidth of the light emitting element to reduce an alignment error betweenthe lens and the light emitting element.

The lens includes a lower surface having the concave part and an uppersurface through which light incident on a light incident surface of theconcave part is emitted. The light incident surface of the lens is aninner surface of the concave part and is defined by a shape of theconcave part. The light incident surface of the lens may include anupper end surface and side surfaces connected from the upper end surfaceto the inlet of the concave part. The concave part may have a shapehaving a width narrowed upward from the inlet thereof to the upper endsurface. The side surface may be an inclined surface having apredetermined gradient from the inlet of the concave part to the upperend surface, but may be a bent inclined surface having a reducedgradient from the inlet to the upper end surface. The upper end surfacemay be a flat surface, but is not limited thereto and therefore mayinclude a concave surface or a convex surface and may further include alight scattering pattern.

The upper surface of the lens has a shape to diffuse the light incidentinto the lens so that the light has a wide directional distribution. Theupper surface of the lens may have a concave surface disposed near acentral axis and a convex surface connected from the concave surface.Unlike this, the upper surface of the lens may have the flat surfacedisposed near the central axis and the convex surface connected from theflat surface. The shape of the upper end surface may include the flatsurface instead of the concave surface according to the related art orthe light scattering pattern, and the like to reduce the influence onthe directional distribution of light even though the central axes ofthe light emitting element and the lens are mis-aligned, therebyincreasing an alignment tolerance between the light emitting element andthe lens.

Meanwhile, the lower surface of the lens includes a flat surfaceenclosing the concave part and an inclined surface enclosing the flatsurface. The flat surface adheres to the circuit board. When areflection sheet is disposed on the circuit board, the flat surfaceadheres to the reflection sheet. Meanwhile, the inclined surface isinclined upward from the flat surface and has a gradient less thanapproximately 10° with respect to the flat surface. Therefore, it ispossible to reduce the loss of light due to internal total reflectioninside the lens and diffuse light at a wide directional distribution byusing the inclined surface.

Meanwhile, the lower surface of the lens may be provided with leg parts.The leg parts may be formed on the inclined surface. The leg parts ofthe lens are attached to the circuit board.

An exemplary embodiment of the present invention also discloses a firstconductive type semiconductor layer; a plurality of mesas disposed onthe first conductive type semiconductor layer, spaced apart from eachother and each including an active layer and a second conductive typesemiconductor layer; reflection electrodes disposed on the plurality ofmesas to ohmic-contact the second conductive type semiconductor layer; acurrent diffusing layer covering the plurality of mesas and the firstconductive type semiconductor layer, disposed within upper areas of eachmesa, having openings which expose the reflection electrodes,ohmic-contacting the first conductive type semiconductor layer, andinsulated from the plurality of mesas, in which the light emitting diodechips is flip-bonded with the circuit board.

The current diffusing layer covers the plurality of mesas and the firstconductive type semiconductor layer and thus the current diffusing layerimproves current diffusing performance.

The first conductive type semiconductor layer is continuous. Further,the plurality of mesas may have elongated shapes extending in parallelwith each other in one direction and the openings of the currentdiffusing layer may be disposed to be biased to the same end side of theplurality of mesas. Therefore, pads connecting between the reflectionelectrodes exposed through the openings of the current diffusing layermay be easily formed.

The current diffusing layer may include reflection metal such as Al.Therefore, in addition to light reflection by the reflection electrodes,the light reflection by the current diffusing layer may be obtained andtherefore light progressed through side walls of the plurality of mesasand the first conductive type semiconductor layer may be reflected.

Meanwhile, the reflection electrodes may each include a reflection metallayer and a barrier metal layer. Further, the barrier metal layer maycover an upper surface and side surfaces of the reflection metal layer.Therefore, it is possible to prevent the reflection metal layer fromdeteriorating by preventing the reflection metal layer from beingexposed to the outside.

The light emitting diode chip may further include: an upper insulatinglayer covering at least a portion of the current diffusing layer andhaving the openings through which the reflection electrodes are exposed;a second pad disposed on the upper insulating layer and being connectedto the exposed reflection electrodes through the openings of the upperinsulating layer; and a first pad connected to the current diffusinglayer. The first pad and the second pad may be formed to have the sameshape and size to easily perform the flip-chip bonding.

Further, the light emitting diode chip may further include a lowerinsulating layer disposed between the plurality of mesas and the currentdiffusing layer to insulate the current diffusing layer from theplurality of mesas. The lower insulating layer may have openingsdisposed within upper areas of each mesa and exposing the reflectionelectrodes.

Further, the openings of the current diffusing layer may each have awidth wider than that of the openings of the lower insulating layer sothat all the openings of the lower insulating layer are exposed. Thatis, side walls of the openings of the current diffusing layer aredisposed on the lower insulating layer. In addition, the light emittingdiode chip may further include an upper insulating layer covering atleast a portion of the current diffusing layer and including theopenings exposing the reflection electrodes. The upper insulating layermay cover the side walls of the openings of the current diffusing layer.

The lower insulating layer may be a reflective dielectric layer, forexample, a distributed Bragg reflector (DBR).

Meanwhile, the light emitting diode chip may further include a growthsubstrate and the growth substrate may be, for example, a sapphiresubstrate or a gallium nitride substrate. The wavelength conversionlayer covers the growth substrate to convert a wavelength of lightemitted from the growth substrate to the outside.

An exemplary embodiment of the present invention also discloses aconcave part defining a light incident surface on which light isincident and a light emitting surface through which the light incidenton the lens is emitted and at least one of the light incident surface ofthe concave part and the light emitting surface includes a plurality ofsections which are at a position of 15° or more from the central axisand are sequentially connected in a height direction.

Adjacent sections of the plurality of sections may have differentcurvatures. Further, the plurality of sections include first, second,and third sections sequentially connected and a vertical directionheight of the first, second, and third sections may be equal to or morethan 1 μm and may be less than a width of the light emitting element.Further, the vertical direction height of each of the plurality ofsections may be equal to or more than 1 μm and may be less than thewidth of the light emitting element.

A plurality of color separations are generated in a spatial colordistribution of light having different wavelengths by the plurality ofsections and the plurality of light emitting elements and the pluralityof lens are arranged to make areas in which the color separation isgenerated overlap each other, thereby implementing the uniform spatialcolor distribution.

The concave part and the light emitting surface of the lens may have arotating body shape with respect to the central axis.

Meanwhile, a virtual reference surface having a single curvature may goacross the first, second, and third sections, respectively. Further, adistance between points on the first, second, and third sections and thevirtual reference surface having the single curvature may be about 10μm, or preferably, about 5 μm.

Further, the light emitting surface may have the convex part having awidth narrowed upward and the concave part having a width narrowedupward and the concave part may be positioned to be closer to thecentral axis than the convex part. Further, the sections of the concavepart may have a height lower than that of the sections of the convexpart.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate exemplary embodiments of theinvention, and together with the description serve to explain theprinciples of the invention.

FIG. 1A is a cross-sectional view for describing a light emitting moduleaccording to the related art.

FIG. 1B is a perspective view of a lens adopted in the light emittingmodule according to the related art.

FIG. 2A is a cross-sectional view for describing a light emitting moduleaccording to an exemplary embodiment of the present invention.

FIG. 2B is a perspective view of a lens adopted in the light emittingmodule according to the exemplary embodiment of the present invention.

FIG. 2C is a schematic diagram for describing a shape of a concave partof a lens according to the exemplary embodiment of the presentinvention.

FIG. 2D is a partially enlarged cross-sectional view of the lens adoptedin the light emitting module according to the exemplary embodiment ofthe present invention.

FIGS. 3A to 3D are cross-sectional views for describing various changeexamples of the concave part of the lens according to exemplaryembodiments of the present invention.

FIG. 4 is a cross-sectional view for describing another change exampleof the lens according to an exemplary embodiment of the presentinvention.

FIG. 5 is a cross-sectional view for describing another change exampleof the lens according to an exemplary embodiment of the presentinvention.

FIG. 6 is a schematic cross-sectional view for describing a lightemitting element according to an exemplary embodiment of the presentinvention;

FIGS. 7A to 12 are diagrams for describing a method for manufacturing alight emitting diode chip which may be used in the light emittingelement according to exemplary embodiments of the present invention, inwhich A in each drawing are plan views and B in each drawing arecross-sectional views taken along the line A-A.

FIGS. 13A and 13B are graphs illustrating directional distributions of alight emitting diode package according to the related art, and aflip-chip type light emitting diode chip having a conformal coatinglayer according to an exemplary embodiment of the present invention,respectively.

FIGS. 14A and 14B are graphs illustrating directional distributions ofthe light emitting module using the light emitting diode packageaccording to the related art, and the light emitting module comprisingthe flip-chip type light emitting diode chip having the conformalcoating layer according to an exemplary embodiment of the presentinvention, respectively.

FIGS. 15A to 15C are schematic diagrams for describing a light emittingdirection depending on various gradients of an inclined surface of alower surface of the lens.

FIGS. 16A and 16B are graphs illustrating a light emitting angledepending on various gradients of the inclined surface of the lowersurface of the lens.

FIG. 17 is a graph illustrating a light spectrum of a light emittingelement according to an exemplary embodiment of the present invention.

FIG. 18 is a graph illustrating light directional distribution of bluelight and yellow light, respectively, of the light emitting elementaccording to the exemplary embodiment of the present invention.

FIG. 19 is a cross-sectional view for describing a lens according to anexemplary embodiment of the present invention.

FIG. 20 is a schematically partially enlarged cross-sectional view fordescribing a light incident surface of the lens of FIG. 19.

FIG. 21 is a schematically partially enlarged cross-sectional view fordescribing a light emitting surface of the lens of FIG. 19.

FIG. 22 is a schematic diagram for describing a color distribution oflight implemented by the lens of FIG. 19.

FIGS. 23A and 23B are simulation diagrams for describing a spatialdistribution of light, in which FIG. 23A illustrates the spatialdistribution of light in the case in which a plurality of sections isnot formed and FIG. 23B illustrates the spatial distribution of light inthe case in which the plurality of sections is formed.

FIG. 24A is a photograph of the actually implemented color distributionof light from the light emitting module in which the plurality of lightemitting elements is coupled with the lens of FIG. 19, and FIG. 24B isan enlarged photograph of a portion of FIG. 24A.

FIG. 25 is a photograph for describing a color distribution of a lightemitting module in which the plurality of light emitting elements iscoupled with the lens of FIG. 19.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Hereinafter, exemplary embodiments of the present invention will bedescribed in detail with reference to the accompanying drawings. Theexemplary embodiments of the present invention to be described below areprovided by way of example so that the idea of the present invention canbe sufficiently transferred to those skilled in the art to which thepresent invention pertains. Therefore, the present invention is notlimited to the exemplary embodiments set forth herein but may bemodified in many different forms. In the accompanying drawings, widths,lengths, thicknesses, or the like, of components may be exaggerated forconvenience. Like reference numerals denote like elements throughout thespecification.

It will be understood that when an element or layer is referred to asbeing “on” or “connected to” another element or layer, it can bedirectly on or directly connected to the other element or layer, orintervening elements or layers may be present. In contrast, when anelement is referred to as being “directly on” or “directly connected to”another element or layer, there are no intervening elements or layerspresent. It will be understood that for the purposes of this disclosure,“at least one of X, Y, and Z” can be construed as X only, Y only, Zonly, or any combination of two or more items X, Y, and Z (e.g., XYZ,XYY, YZ, ZZ).

Spatially relative terms, such as “beneath”, “below”, “lower”, “above”,“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

FIG. 2A is a cross-sectional view for describing a light emitting moduleaccording to an exemplary embodiment of the present invention, FIG. 2Bis a perspective view of a lens 300 a of the light emitting module, FIG.2C is a schematic diagram for describing a concave part 320 of the lens300 a, and FIG. 2D is a partially enlarged cross-sectional view fordescribing a lower surface 310 of the lens 300 a.

Referring first to FIG. 2A, the light emitting module includes a circuitboard 100 a, a light emitting element 200 a, and the lens 300 a.Further, the light emitting module may include a reflection sheet 110.

The circuit board 100 a is a printed circuit board on which a circuitpattern is formed. Here, the case in which one light emitting element200 a is mounted on the circuit board 100 a is illustrated, but aplurality of light emitting elements 200 a may be aligned on the circuitboard 100 a and the lens 300 a may be disposed over each light emittingelement 200 a.

Unlike the light emitting diode package according to the related art,the light emitting element 200 a does not have a chip mounting memberfor mounting a light emitting diode chip and is directly mounted on thecircuit board 100 a by flip bonding, without using a bonding wire. Thatis, the circuit board 100 a performs a function of the chip mountingmember for mounting the light emitting diode chip. The light emittingelement 200 a does not use the bonding wire and therefore does notrequire a molding part for protecting the wire. The light emittingelement 200 a according to exemplary embodiments of the presentinvention will be described below in detail with reference to FIG. 6.

The reflection sheet 110 is disposed between the lens 300 a and thecircuit board 100 a. The reflection sheet 110 may be coated with a whitereflection material having high reflectivity so as to reflect lighthaving a wide wavelength range of a visible area. The reflection sheet110 reflects light, which is emitted toward the circuit board 100 aside, into the lens 300 a.

The lens 300 a may include a lower surface 310 and an upper surface 350and may further include a flange 370 and leg parts 390. The lowersurface 310 includes a concave part 320, a flat surface 310 a enclosingthe concave part 320, and an inclined surface 310 b enclosing the flatsurface 310 a.

The concave part 320 defines a light incident surface 330 through whichlight is incident from the light emitting element 200 a into the lens300 a. That is, the light incident surface 330 is an inner surface ofthe concave part 320. The light incident surface 330 includes a sidesurface 330 a and an upper end surface 330 b. The concave part 320 has ashape narrowed upward from an inlet. The side surface 330 a may be aninclined surface having a predetermined gradient from the inlet to theupper end surface 330 b, and to the contrary, may be an inclined surfacehaving a reduced gradient from the inlet to the upper end surface 330 b.That is, as illustrated in FIG. 2C, the side surface 330 a is shown by astraight line or a curved line protruding upward in a verticalcross-sectional view.

The light emitting element 200 a is substantially disposed inside theconcave part 320. To this end, a width W1 of the inlet of the concavepart 320 is wider than a width w of the light emitting element 200 a.Meanwhile, the width W1 of the inlet of the concave part 320 is lessthan three times the width w of the light emitting element 200 a.According to the exemplary embodiments of the present invention, thelight emitting element 200 a has a relatively smaller size than thelight emitting element 200 according to the related art, and thereforethere is a need to precisely align the light emitting element 200 a andthe lens 300 a. Therefore, the width W1 of the inlet of the concave part320 is less than three times the width w of the light emitting element200 a and in addition, is set to be equal to or less than twice thewidth w of the light emitting element 200 a, thereby preventing the lens300 a and the light emitting element 200 a from mis-aligning. Further, adistance between the light emitting element 200 a and the light incidentsurface 330 is closed to reduce a quantity of light output to theoutside.

Meanwhile, the upper end surface 330 b of the light incident surface 330according to the present exemplary embodiment has a flat shape. A widthW2 of the upper end surface 330 b is smaller than the width W1 of theinlet and is smaller than the width w of the light emitting element 200a. The width W2 of the upper end surface 330 b may be determined so thatan angle cc formed by a straight line connecting from a center of theinlet of the concave part 320 to an edge of the upper end surface 330 balong a central axis is at least 3°, or preferably, 6°. Light having anangle of beam spread ranging from +15° to −15° among the light emittedfrom the light emitting element 200 a is incident on at least upper endsurface 330 b, thereby improving diffusibility of light.

When a central axis of the light emitting element 200 a and the lens 300a is not precisely aligned, the upper end surface 330 b prevents adirectional distribution of the light emitted to the outside of the lens300 a from being greatly changed.

Meanwhile, a height H of the concave part 320 may be controlleddepending on the angle of beam spread of the light emitting element 200a, a shape of the upper surface 350 of the lens 300 a, the requireddirectional distribution of light, and the like. However, according tothe present exemplary embodiment, the height H of the concave part 320may have a relatively smaller value than the lens according to therelated art as the width W1 of the inlet of the concave part 320 isreduced. In particular, the height H of the concave part 320 may besmaller than a thickness of the flange 370.

Referring back to FIG. 2A, the upper surface 350 of the lens 300 a has ashape to diffuse light incident into the lens 300 a so that the lighthas a wide directional distribution. For example, the upper surface 350of the lens 300 a may have a concave surface 350 a disposed near thecentral axis and a convex surface 350 b connected to the concavesurface. The concave surface 350 a diffuses the light emitted near thecentral axis of the lens 300 a to the outside, and the convex surface350 b increases a quantity of light emitted outside the central axis ofthe lens 300 a.

Meanwhile, the flange 370 connects the upper surface 350 to the lowersurface 310 and limits a size of an appearance of the lens. The sidesurfaces of the flange 370 and the lower surface 310 may be formed withrugged patterns. Meanwhile, the leg part 390 of the lens 300 a iscoupled with the circuit board 100 a to fix the lens 300 a. Each end ofthe leg parts 390 may be bonded on the circuit board 100 a by, forexample, an adhesive or may be fitted in holes formed on the circuitboard 100 a.

Meanwhile, as illustrated in FIG. 2B, there may be four leg parts 390.However, there may be other number of leg parts 390, such as three as inthe related art. As illustrated in FIG. 2D, the leg parts 390 may beformed on the inclined surface 310 b.

Referring to FIGS. 2A and 2D, the lower surface 310 of the lens 300 aincludes the flat surface 310 a enclosing the concave part 320, and aninclined surface 310 b enclosing the flat surface 310 a. The flatsurface 310 a adheres to the circuit board 100 a or the reflection sheet110, and as a result, it is possible to prevent a loss of light at thelower surface of the lens 300 a. In FIG. 2D, a radius of the lens 300 ais represented by d/2, a length of the flat surface 310 a from the lightincident surface 330 to the inclined surface 310 b is represented byb_(o), and a radial length of the inclined surface 310 b is representedby b_(x).

Meanwhile, the inclined surface 310 b is inclined upward, having aninclined angle β to the flat surface 310 a. The inclined surface 310 bis connected to the side surfaces of the lens 300 a, for example, theside surfaces of the flange 370. Therefore, the side surfaces of thelens 300 a are positioned at an upper portion by a height h from theflat surface 310 a. The inclined angle β of the inclined surface 310 bmay be less than 10°. This will be described below in detail withreference to FIGS. 15 and 16.

FIGS. 3A to 3D are cross-sectional views for describing various changeexamples of the lens according to exemplary embodiments of the presentinvention. Here, various change examples of the concave part 320 of FIG.1 will be described.

In FIG. 3A, a portion near the central axis C of the lens 300 a in theupper end surface 330 b described in FIG. 1 forms a surface protrudingdownward. The protruding surface may primarily control the lightincident near the central axis.

FIG. 3B is similar to FIG. 3A, but differs from FIG. 3A in that avertical surface to the central axis in the upper end surface of FIG. 3Aprotrudes upward. The upper end surface has both of the surfaceprotruding upward and the surface protruding downward and thus thechange in the directional distribution of light due to an alignmenterror between the light emitting element and the lens may be mitigated.

In FIG. 3C, a portion near the central axis C in the upper end surface330 b described in FIG. 1 forms a surface protruding upward. Theprotruding surface may better diffuse the light incident near thecentral axis C.

FIG. 3D is similar to FIG. 3C, but differs from FIG. 3C in that avertical surface to the central axis C in the upper end surface of FIG.3D protrudes downward. The upper end surface has both of the surfaceprotruding upward and the surface protruding downward and thus thechange in the directional distribution of light due to an alignmenterror between the light emitting element and the lens may be mitigated.

FIG. 4 is a cross-sectional view for describing a change example of alens according to another exemplary embodiment of the present invention.

Referring to FIG. 4, a light scattering pattern 330 c is formed on theupper end surface 330 b. The light scattering pattern 330 c may beformed as a rugged pattern.

Generally, a relatively large amount of light flux is concentrated nearthe central axis C of the lens. In addition, according to the presentexemplary embodiment, the upper end surface 330 b is a surface verticalto the central axis C and therefore the light flux may be moreconcentrated near the central axis C. Therefore, the light scatteringpattern 330 c is formed on the upper end surface 330 b to be able tobetter diffuse the light flux near a central axis C.

FIG. 5 is a cross-sectional view for describing a change example of alens according to another exemplary embodiment of the present invention.

Referring to FIG. 5, a lens 400 a according to the present exemplaryembodiment is substantially similar to the lens 300 a described withreference to FIGS. 2A to 2D, but has a different shape of an uppersurface 450 and a position of leg parts 490. That is, instead of aconcave surface 350 a of FIG. 2A, a relatively flat surface 450 a isdisposed near a central axis of the lens 400 a, and a convex surface 450b is connected outwardly from the flat surface 450 a. Meanwhile, the legparts 490 are disposed near side surfaces of the lens 400 a.

The shape of the lens may be variously changed in consideration of thedesired directional distribution of light, and the like.

FIG. 6 is a schematic cross-sectional view for describing the lightemitting element 200 a according to an exemplary embodiment of thepresent invention.

Referring to FIG. 6, the light emitting element 200 a includes the lightemitting diode chip 210 and the wavelength conversion layer 240. Thelight emitting diode chip 210 includes a substrate 211 and asemiconductor laminate 213 and may further include electrode pads 215 aand 215 b.

The light emitting diode chip 210 is a flip-chip and the electrode pads215 a and 215 b are disposed under the light emitting diode chip 210.The width w of the light emitting diode chip 210 may range fromapproximately 0.7 to 1.5 mm.

The substrate 211 may be a growth substrate for growing a semiconductorlayer, for example, a sapphire substrate or a gallium nitride substrate.In particular, when the substrate 211 is the sapphire substrate, arefractive index is gradually reduced toward the semiconductor laminate213, the sapphire substrate 211, and the wavelength conversion layer240, thereby improving light extraction efficiency. According to analternative embodiment, the substrate 211 may be omitted.

The semiconductor laminate 213 is formed of a gallium nitride-basedcompound semiconductor and may emit ultraviolet or blue wavelengthlight.

The light emitting diode chip 210 is directly mounted on the circuitboard 110 a. The light emitting diode chip 210 is flip-bonded withoutusing a bonding wire and is directly connected to the printed circuit onthe circuit board 100 a. According to the present exemplary embodiment,since a wire is not used at the time of bonding the light emitting diodechip 210 on the circuit board 100 a, there is no need for a molding partfor protecting the wire and there is no need to partially remove thewavelength conversion layer 240 to expose a bonding pad. Therefore, inthe light emitting diode chip 210 according to the present exemplaryembodiment, a color deviation or a luminous speck phenomenon may bealleviated and the module manufacturing process may be simplifiedcompared to using a light emitting diode chip using the bonding wire.

The flip-chip type light emitting diode chip according to the presentexemplary embodiment will be described below in detail with reference toFIGS. 7 to 12.

The wavelength conversion layer 240 covers the light emitting diode chip210. As illustrated, the conformal coated wavelength conversion layer240, for example, a phosphor layer may be formed on the light emittingdiode chip 210 and may wavelength-convert the light emitted from thelight emitting diode chip 210. The wavelength conversion layer 240 iscoated on the light emitting diode chip 210 and may cover the uppersurface and the side surfaces of the light emitting diode chip 210.According to an alternative embodiment, the wavelength conversion layer240 may also cover only the upper surface of the light emitting diodechip 210. Light having various colors may be implemented by using thelight emitted from the light emitting diode chip 210 and the wavelengthconversion layer 240, and in particular, mixed light such as white lightmay be implemented.

According to the present exemplary embodiment, the conformal coatedwavelength conversion layer 240 is formed on the light emitting diodechip 210 in advance and thus may be mounted on the circuit board 100 aalong with the light emitting diode chip 210.

Hereinafter, the method of manufacturing the light emitting diode chip210 will be described.

FIGS. 7 to 11 are diagrams for describing a method for manufacturing aflip-chip type light emitting diode chip according to the presentexemplary embodiment, in which FIGS. 7A, 8A, 9A, 10A, and 11A are planviews and FIGS. 7B, 8B, 9B, 10B, and 11B are cross-sectional views takenalong the line A-A.

Referring first to FIGS. 7A and 7B, a first conductivity typesemiconductor layer 23 is formed on a growth substrate 21 and aplurality of mesas M spaced apart from each other are formed on thefirst conductivity type semiconductor layer 23. The plurality of mesas Meach include an active layer 25 and a second conductivity typesemiconductor layer 27. The active layer 25 is disposed between thefirst conductivity type semiconductor layer 23 and the secondconductivity type semiconductor layer 27. Meanwhile, reflectionelectrodes 30 are each disposed on the plurality of mesas M.

The plurality of mesas M may be formed by growing an epitaxial layerwhich includes the first conductivity type semiconductor layer 23, theactive layer 25, and the second conductivity type semiconductor layer27, on the growth substrate 21 using a metal organic chemical vapordeposition method, or the like, and then patterning the secondconductivity type semiconductor layer 27 and the active layer 25 toexpose the first conductivity type semiconductor layer 23. The sidesurfaces of the plurality of mesas M may be formed to be inclined byusing a technology such as photoresist reflow. An inclined profile ofthe side surfaces of the mesa M improves the light extraction efficiencygenerated from the active layer 25.

As illustrated, the plurality of mesas M may have an elongated shapeextending in parallel with each other in one direction. The shapesimplifies a process of forming the plurality of mesas M having the sameshape in the plurality of chip areas on the growth substrate 21.

The reflection electrodes 30 may be formed on each mesa M after formingthe plurality of mesas M, and therefore may be formed on the secondconductivity type semiconductor layer 27 in advance prior to growing thesecond conductivity type semiconductor layer 27 and forming the mesas M.The reflection electrode 30 covers most of the upper surface of the mesaM and has substantially the same shape as a plane shape of the mesa M.

The reflection electrodes 30 include a reflection layer 28 and mayfurther include a barrier layer 29. The barrier layer 29 may cover anupper surface and side surfaces of the reflection layer 28. For example,a pattern of the reflection layer 28 is formed, the barrier layer 29 isformed thereon, and thus the barrier layer 29 may be formed to cover theupper surface and the side surfaces of the reflection layer 28. Forexample, the reflection layer 28 may be formed by depositing andpatterning Ag, Ag alloy, Ni/Ag, NiZn/Ag, and TiO/Ag layers. Meanwhile,the barrier layer 29 may be formed of a layer of Ni, Cr, Ti, Pt, Rd, Ru,W, Mo, TiW, or a composite layer thereof, and prevents a metal materialof the reflection layer from being diffused or polluted.

After the plurality of mesas M are formed, an edge of the firstconductivity type semiconductor layer 23 may also be etched. Therefore,the upper surface of the substrate 21 may be exposed. The side surfacesof the first conductivity type semiconductor layer 23 may also be formedto be inclined.

As illustrated in FIG. 7, the plurality of mesas M may be disposed on anupper area of the first conductivity type semiconductor layer 23. Thatis, the plurality of mesas M may be disposed on the upper area of thefirst conductivity type semiconductor layer 23 in an island form. Asillustrated in FIG. 12, the mesas M extending in one direction may beformed to reach an upper edge of the first conductivity typesemiconductor layer 23. That is, the edges in one direction of the lowersurfaces of the plurality of mesas M coincide with the edges of thefirst conductivity type semiconductor layer 23 in one direction.Therefore, the upper surface of the first conductivity typesemiconductor layer 23 is partitioned by the plurality of mesas M.

Referring to FIGS. 8A and 8B, a lower insulating layer 31 covering theplurality of mesas M and the first conductivity type semiconductor layer23 is formed. The lower insulating layer 31 has openings 31 a and 31 bthrough which the lower insulating layer may be electrically connectedto the first conductivity type semiconductor layer 23 and the secondconductivity type semiconductor layer 27 in the specific area. Forexample, the lower insulating layer 31 may have the openings 31 athrough which the first conductivity type semiconductor layer 23 isexposed and the openings 31 b through which the reflection electrodes 30are exposed.

The openings 31 a may be disposed in an area between the mesas M andnear the edge of the substrate 21 and may have an elongated shapedextending along the mesas M. Meanwhile, the openings 31 b are disposedover the mesas M and are biased to the same end sides of the mesas.

The lower insulating layer 31 may be formed of an oxide layer of SiO₂,and the like, a nitride layer of SiNx, and the like, and an insulatinglayer of SiON and MgF₂, by using chemical vapor deposition (CVD), andthe like. The lower insulating layer 31 may be formed of a single layeror a multi-layer. Further, the lower insulating layer 31 may be formedof a distributed Bragg reflector (DBR) in which a low refractivematerial layer and a high refractive material layer are alternatelystacked. For example, an insulating reflection layer having highreflectivity may be formed by stacking a dielectric layer of SiO₂/TiO₂,SiO₂/Nb₂O₅, or the like.

Referring to FIGS. 9A and 9B, a current diffusing layer 33 is formed onthe lower insulating layer 31. The current diffusing layer 33 covers theplurality of mesas M and the first conductivity type semiconductor layer23. Further, the current diffusing layers 33 are disposed within theupper areas of the plurality of mesas M, respectively and have openings33 a through which the reflection electrodes are exposed. The currentdiffusing layer 33 may ohmic-contact the first conductivity typesemiconductor layer 23 through the openings 31 a of the lower insulatinglayer 31. The current diffusing layer 33 is insulated from the pluralityof mesas M and the reflection electrodes 30 by the lower insulatinglayer 31.

The openings 33 a of the current diffusing layer 33 each have an areawider than that of the openings 31 b of the lower insulating layer 31 soas to prevent the current diffusing layer 33 from connecting to thereflection electrodes 30. Therefore, side walls of the openings 33 a aredisposed on the lower insulating layer 31.

The current diffusing layer 33 is formed on the upper portion of almostall the area of the substrate 21 other than the openings 33 a.Therefore, a current may be easily diffused through the currentdiffusing layer 33. The current diffusing layer 33 may include a highreflection metal layer such as an Al layer and the high reflection metallayer may be formed on an adhesive layer of Ti, Cr, Ni, or the like.Further, a protective layer having a single layer structure or acomposite layer structure of Ni, Cr, Au, and the like may be formed onthe high reflection metal layer. The current diffusing layer 33 may havea multi-layer structure of, for example, Ti/Al/Ti/Ni/Au.

Referring to FIGS. 10A and 10B, an upper insulating layer 35 is formedon the current diffusing layer 33. The upper insulating layer 35 hasopenings 35 b through which the reflection electrodes 30 are exposed,along with the opening 35 a through which the current diffusing layer 33is exposed. The openings 35 a may have an elongated shape in a directionperpendicular to a length direction of the mesas M, and have an arearelatively wider than that of the openings 35 b. The openings 35 bexpose the reflection electrodes 30, which are exposed through theopenings 33 a of the current diffusing layer 33 and the openings 31 b ofthe lower insulating layer 31. The openings 35 b have an area narrowerthan that of the openings 33 a of the current diffusing layer 33 and mayhave an area wider than that of the openings 31 b of the lowerinsulating layer 31. Therefore, the side walls of the openings 33 a ofthe current distributing layer 33 may be covered with the upperinsulating layer 35.

The upper insulating layer 35 may be formed of an oxide insulatinglayer, a nitride insulating layer, a mixed layer of these insulatinglayers, or an intersecting layer or may be made of a polymer such aspolyimide, polytetrafluoroethylene (PTFE), and parylene.

Referring to FIGS. 11A and 11B, a first pad 37 a and a second pad 37 bare formed on the upper insulating layer 35. The first pad 37 a isconnected to the current diffusing layer 33 through the opening 35 a ofthe upper insulating layer 35 and the second pad 37 b is connected tothe reflection electrodes 30 through the openings 35 b of the upperinsulating layer 35. The first pad 37 a and the second pad 37 b mayconnect bumps for mounting light emitting diodes on the circuit board,and the like or may be used as a pad for SMT.

The first and second pads 37 a and 37 b may be formed by the sameprocess and may be formed using, for example, a photolithography and/oretching or a lift off technology. The first and second pads 37 a and 37b may include, for example, an adhesive layer of Ti, Cr, Ni, or thelike, and a high conductivity metal layer of Al, Cu, Ag, Au, or thelike. Ends of the first and second pads 37 a and 37 b may be formed tobe disposed on the same plane, and therefore the light emitting diodechip 210 may be flip-bonded on conductive patterns which are formed tohave the same height on the circuit boards 100 a.

Next, the light emitting diode chip is completed by dividing the growthsubstrate 21 in an individual light emitting diode chip unit. The growthsubstrate 21 may also be removed from the light emitting diode chipbefore or after being divided in the individual light emitting diodechip unit.

Hereinafter, a structure of the light emitting diode chip according tothe present exemplary embodiment will be described in detail withreference to FIGS. 11A and 11B.

The light emitting diode chip includes the first conductivity typesemiconductor layer 23, the mesas M, the reflection electrodes 30, andthe current diffusing layer 33, and may include the growth substrate 21,the lower insulating layer 31, the upper insulating layer 35, the firstpad 37 a, and the second pad 37 b.

The substrate 21 may be a growth substrate for growing galliumnitride-based epitaxial layers, for example, a sapphire substrate or agallium nitride substrate. The substrate 21 is, for example, thesapphire substrate and may have a thickness of 200 μm or more, orpreferably, a thickness of 250 μm or more.

The first conductivity type semiconductor layer 23 is continuous and theplurality of mesas M are disposed on the first conductivity typesemiconductor layer 23, spaced apart from each other. As described withreference to FIG. 7, the mesas M include the active layer 25 and thesecond conductivity type semiconductor layer 27 and have an elongatedshape extending toward one side. Here, the mesas M have a stackedstructure of the gallium nitride-based compound semiconductor. Asillustrated in FIG. 7, the mesas M may be disposed within the upper areaof the first conductive type semiconductor layer 23. Unlike this, asillustrated in FIG. 12, the mesas M may extend to an edge of the uppersurface of the first conductivity type semiconductor layer 23 along onedirection, and therefore the upper surface of the first conductivitytype semiconductor layer 23 may be partitioned into a plurality ofareas. Therefore, the current diffusing performance may be enhanced bymitigating the concentration of current near corners of the mesas M.

The reflection electrodes 30 each are disposed on the plurality of mesasM to ohmic-contact the second conductivity type semiconductor layer 27.As described with reference to FIG. 7, the reflection electrodes 300 mayinclude the reflection layer 28 and the barrier layer 29, in which thebarrier layer 29 may cover the upper surface and the side surfaces ofthe reflection layer 28.

The current diffusing layer 33 covers the plurality of mesas M and thefirst conductivity type semiconductor layer 23. The current diffusinglayers 33 are disposed within the upper areas of the plurality of mesasM, respectively, and have the openings 33 a through which the reflectionelectrodes 30 are exposed. The current diffusing layer 33 furtherohmic-contacts the first conductivity type semiconductor layer 23 and isinsulated from the plurality of mesas M. The current diffusing layer 33may include a reflection metal such as Al.

The current diffusing layer 33 may be insulated from the plurality ofmesas M by the lower insulating layer 31. For example, the lowerinsulating layer 31 may be disposed between the plurality of mesas M andthe current diffusing layer 33 to insulate the current diffusing layer33 from the plurality of mesas M. Further, the lower insulating layer 31may be disposed within the upper areas of the mesas M, respectively, andhave the openings 31 b through which the reflection electrodes 30 areexposed, and may have the openings 31 a through which the firstconductivity type semiconductor layer 23 is exposed. The currentdiffusing layer 33 may be connected to the first conductivity typesemiconductor layer 23 through the openings 31 a. The openings 31 b ofthe lower insulating layer 31 have an area narrower than that of theopenings 33 a of the current diffusing layer 33, and all are exposed bythe openings 33 a.

The upper insulating layer 35 covers at least a portion of the currentdiffusing layer 33. Further, the upper insulating layer 35 has openings35 b through which the reflection electrodes 30 are exposed. Further,the upper insulating layer 35 may have opening 35 a through which thecurrent diffusing layer 33 is exposed. The upper insulating layer 35 maycover the side walls of the openings 33 a of the current diffusing layer33.

The first pad 37 a may be disposed on the current diffusing layer 33 andmay be connected to the current diffusing layer 33 through, for example,the opening 35 a of the upper insulating layer 35. Further, the secondpad 37 b is connected to the reflection electrodes 30 exposed throughthe openings 35 b. As illustrated in FIGS. 11A and 11B, the upper endsof the first pad 37 a and the second pad 37 b may be positioned at thesame height.

According to the present exemplary embodiment, the current diffusinglayer 33 covers the mesas M and almost all the area of the firstconductivity type semiconductor layer 23 between the mesas M. Therefore,a current may be easily diffused through the current diffusing layer 33.

Further, the current diffusing layer 33 includes the reflection metallayer such as Al or the lower insulating layer is formed as theinsulating reflection layer to reflect the light not reflected by thereflection electrodes 30 using the current diffusing layer 33 or thelower insulating layer 31, thereby improving the light extractionefficiency.

The flip-chip type light emitting diode chip according to the presentexemplary embodiment may have wide directional distribution of light, asdescribed below.

FIGS. 13A and 13B are graphs illustrating the directional distributionof the light emitting diode package 200 according to the related art andthe flip-chip type light emitting diode chip 210 having the lightemitting element, that is, the conformal coating layer 240 according tothe exemplary embodiment of the present invention described above withrespect to FIGS. 6-12.

Referring to FIG. 13A, the light emitting diode package 200 according tothe related art has an angle of beam spread of about 120°. The lightemitting element according to the exemplary embodiment described withrespect to FIGS. 6-12 has an angle of beam spread of about 145°, asillustrated in FIG. 13B. That is, it may be appreciated that the chiplevel light emitting element according to the present exemplaryembodiment has an angle of beam spread increased by about 25° comparedto the package level light emitting element according to the relatedart.

FIG. 14A illustrates the directional distribution of the light emittingmodule using the light emitting diode package according to the relatedart having the angle of beam spread of 120°, and FIG. 14B illustratesthe directional distribution of the light emitting module using theflip-chip type light emitting diode chip 210 provided with the conformalcoating layer 240 having the angle of beam spread of 145° according tothe present exemplary embodiment. The light directional distribution inone direction is simulated by using the light emitting element and thelens having the same illumination distributions in each direction. Thelight directional distribution represents the luminous intensitydepending on the angle of beam spread at a point spaced by 5 m from eachlight emitting element. Here, the lower surface of the lens is generallyflat without the inclined surface 310 b.

In the graphs shown in FIGS. 14A and 14B, as the angle between maximumluminous intensity values is large and the ratio C/P of the luminousintensity at the center for the maximum luminous intensity value issmall, light is widely distributed and uniformly diffused. In the caseof FIG. 14A, the angle between the maximum luminous intensity values is146° and the ratio of the luminous intensity at the center for themaximum luminous intensity is 10%, and in the case of FIG. 14B, thesevalues each are 152° and 4.5%. Further, compared with an angle at apoint at which the luminous intensity is 50%, in the case of FIG. 14A,the angle is 65°, and in the case of FIG. 14B, the angle is 70°.Therefore, when the light emitting module is manufactured using theflip-chip type light emitting diode chip 210 provided with the conformalcoating layer 240 according to the present exemplary embodiment, thelight emitting module may be wider and may uniformly diffuse lightcompared to the light emitting module according to the related art.

FIGS. 15A to 15C are schematic diagrams for describing a light emittingdirection depending on various gradients of the inclined surface 310 bof the lower surface of the lens.

A beam ray of light emitted at an angle within 0° to 3° with respect tothe flat surface 310 a of the lower surface of the lens from the lowerportion of the side surfaces of the light emitting element 200 a issimulated and an angle γ between the light emitted from the lens 300 aand the flat surface 310 a of the lower surface of the lens iscalculated.

In the case of FIG. 15A, the inclined angle β is about 4° and the angleγ of the beam ray emitted from the lens 300 a is 9°. Therefore, a lightemitting angle 90—γ to the central axis of the lens is 81°.

Meanwhile, in the case of FIG. 15B, the inclined angle β is about 9.5°and the angle γ of the beam ray emitted from the lens 300 a is 24°.Therefore, the light emitting angle 90—γ to the central axis of the lensis 66°.

Meanwhile, in the case of FIG. 15C, the inclined angle β is about 23°and the beam ray emitted from the lens 300 a is totally reflected insidethe lens 300 a to be emitted through the side surface at an oppositeside thereto. In this case, the angle γ is 39°. Therefore, the lightemitting angle 90—γ to the central axis of the lens is 51°.

By performing the simulation in several angles, the angle γ of the beamray depending on various inclined angles β of the inclined surface ofthe lower surface of the lens is calculated, which is represented by thegraph of FIG. 16A and the angle of the graph of FIG. 16A is convertinginto the light emitting angle 90—γ, which is represented by FIG. 16B.

Referring to FIG. 16A or 16B, as the inclined angle β is increased, theangle γ is gradually increased and when the angle β exceeds about 20°,as illustrated in FIG. 15C, it may be appreciated that the internaltotal reflection of light inside the lens is generated. Meanwhile, inthe case in which the inclined angle β is less than 5°, as the inclinedangle β is increased, the angle γ is smoothly increased but in the casein which the inclined angle β is equal to or more than 5°, the angle γis relatively suddenly increased and in the case in which the inclinedangle β is equal to or more than 15°, the angle is converged toapproximately a straight line.

According to the above simulation result, when the inclined angle βexceeds 20°, since the internal total reflection inside the lens 300 ais generated, a loss of light occurs, and since the light emitting angle90—γ has a value less than 70°, light is converged near the central axisof the lens to hinder the implementation of the uniform light.

Meanwhile, when the inclined angle β ranges from about 10° to 20°, thebeam ray is emitted to the outside through the sides of the lens withoutthe internal total reflection, but since the light emitting angle 90—γhas a value less than 70°, light is converged near the central axis ofthe lens to hinder the implementation of the uniform light.

On the other hand, when the inclined angle β is less than 10°, since thelight emitting angle 90—γ exceeds approximately 70°, light may be widelydiffused and therefore the inclined angle β may be less than 10°.

In the case of the light emitting element to which the light emittingdiode chip 210 coated with the wavelength conversion layer 240 asdescribed above is applied, the color deviation may be serious in thespatial color distribution of the light emitting element 200 a due tothe thickness of the wavelength conversion layer 240, the distributionof the phosphor within the wavelength conversion layer 240, thedistribution of light emitted from the light emitting diode chip 210,and the like.

FIG. 17 is a graph illustrating a light spectrum of the light emittingelement 200 a according to an exemplary embodiment of the presentinvention.

Referring to FIG. 17, a mixed light spectrum of blue light of the lightemitting diode chip 210 and yellow light of the phosphor may beobserved. The blue light has a peak wavelength of about 450 nm and theyellow light has a wide spectrum distribution from a green to a redwavelength.

FIG. 18 is a graph illustrating light directional distributions of theblue light and the yellow light, respectively, of the light emittingelement 200 a according to an exemplary embodiment of the presentinvention. The light emitted from the light emitting diode chip 210 isfiltered using a blue light filter and a yellow light filter to measurethe light directional distributions of each light. The light directionaldistribution of the blue light is measured using the blue filter,transmitting light of 400 to 500 nm, and the light directionaldistribution of the yellow light is measured using a yellow filter,transmitting light of 500 to 800 nm.

Referring to FIG. 18, light distributions of blue light B and yellowlight Y are similar to each other near the angle of beam spread of 0°,but in the angle of beam spread which is equal to or more than 15°, thedifference in the light distributions occurs and thus the spatial colordeviation occurs.

When a light diffusion lens is applied to the light emitting element, itmay be necessary to reduce the spatial color deviation. Hereinafter, thelens to minimize the spatial color deviation will be described.

FIG. 19 is a cross-sectional view for describing a lens 600 according toan exemplary embodiment of the present invention, FIG. 20 is a partialenlarged view of a light incident surface 630 of the lens 600, and FIG.21 is a partial enlarged view of an upper surface 650 of the lens 600.

The lens according to the present exemplary embodiment is substantiallysimilar to the lens 300 a described with reference to FIGS. 2A to 2D,but differs from the lens 300 a in that it includes a light incidentsurface 630 of a concave part, a concave part 650 a and a convex part650 b of an upper surface 650, and a plurality of sections 630 a 1 to630 an, 650 a 1 to 650 an, and 650 b 1 to 650 bn. Hereinafter, thedescription overlapping with the lens 300 a described above withreference to FIGS. 2A to 2D will be omitted, and the plurality ofsections 630 a 1 to 630 an, 650 a 1 to 650 an, and 650 b 1 to 650 bnwill be described.

Referring first to FIGS. 19 and 20, adjacent sections of the pluralityof sections 630 a 1 to 630 an may have different curvatures. Thesections having different curvatures are continuously connected toconfigure a side surface 630 a of the light incident surface.

The plurality of sections 630 a 1 to 630 an may include a first section630 a (n-k−1), a second section 630 a (n-k), and a third section 630 a(n-k+1) which are connected to each other in a vertical direction, asillustrated in FIG. 20. A curvature of the second section 630 a (n-k)differs from that of the first section 630 a (n-k−1) and the thirdsection 630 a (n-k+1). Further, the curvature of the first section 630 a(n-k−1) may differ from or be equal to that of the third section 630 a(n-k+1).

Meanwhile, thicknesses a1, a2, and a3 of the first section 630 a(n-k−1), the second section 630 a (n-k), and the third section 630 a(n-k+1), respectively, are equal to or greater than 1 μm and are lessthan the width of the light emitting element 200 a. When the thicknessof each section is less than 1 μm, an interference or diffractionphenomenon of light transmitting each section is serious. Further, whenthe thickness of each section is excessively large, it is difficult toachieve a desired effect.

The thicknesses a1, a2, and a3 of the first section 630 a (n-k−1), thesecond section 630 a (n-k), and the third section 630 a (n-k+1),respectively, may be the same or different from one another. Further,all the vertical direction thicknesses of the plurality of sections 630a 1 to 630 an are equal to or greater than 1 μm and may be smaller thanthe width of the light emitting element 200 a. By making the curvaturesof the adjacent sections different, color separation of the lightincident on the light incident surface 630 may be made depending on thewavelength.

The plurality of sections 630 a 1 to 630 an may be disposed in an areaof 15° or more from the central axis in consideration of the lightdirectional distribution for each spectrum of the light emitting diodechip 210, in particular. That is, the plurality of sections 630 a 1 to630 an is not disposed in the area less than 15° from the central axis.

Meanwhile, as illustrated in FIG. 20, the first section 630 a (n-k−1),the second section 630 a (n-k), and the third section 630 a (n-k+1) maybe sequentially connected to one another so that a virtual referencesurface 630 r having a single curvature goes across the first section630 a (n-k−1), the second section 630 a (n-k), and the third section 630a (n-k+1). The virtual reference surface 630 r having the singlecurvature may be the side surface 330 a of the light incident surface330 of FIG. 2A. Further, a distance between each point on the firstsection 630 a (n-k−1), the second section 630 a (n-k), and the thirdsection 630 a (n-k+1) and the virtual reference surface 630 r does notexceed 10 μm, or preferably, about 5 μm.

Referring to FIGS. 19 and 21, adjacent sections of the plurality ofsections 650 b 1 to 650 bn may have different curvatures. The sectionshaving different curvatures may be continuously connected to configurethe convex part 650 b.

The plurality of sections 650 b 1 to 650 bn include a first section 650b (n-k−1), a second section 650 b (n-k), and a third section 650 b(n-k+1) which are connected to each other in a vertical direction asillustrated in FIG. 21. A curvature of the second section 650 b (n-k)differs from that of the first section 650 b (n-k−1) and the thirdsection 650 b (n-k+1). Further, the curvature of the first section 650 b(n-k−1) may differ from or may be equal to that of the third section 650b (n-k+1).

Meanwhile, thicknesses b1, b2, and b3 of the first section 650 b(n-k−1), the second section 650 b (n-k), and the third section 650 b(n-k+1), respectively, are equal to or greater than 1 μm and are smallerthan the width of the light emitting element 200 a. When the thicknessesof each section are less than 1 μm, an interference or diffractionphenomenon of light transmitting each section is serious. Further, whenthe thicknesses of each section are excessively large, it may bedifficult to achieve a desired effect.

Meanwhile, the thicknesses b1, b2, and b3 of the first section 650 b(n-k−1), the second section 650 b (n-k), and the third section 650 b(n-k+1), respectively, may be the same or different from one another.Further, all the thicknesses of the plurality of sections 650 b 1 to 650bn are equal to or greater than 1 μm and may be smaller than the widthof the light emitting element 200 a. By making the curvatures of theadjacent sections different, the color separation of the light emittedfrom the convex part 650 b may be made depending on the wavelength.

Meanwhile, as illustrated in FIG. 21, the first section 650 b (n-k−1),the second section 650 b (n-k), and the third section 650 b (n-k+1) maybe sequentially connected to one another so that a virtual referencesurface 650 r having a single curvature goes across the first section650 b (n-k−1), the second section 650 b (n-k), and the third section 650b (n-k+1). The virtual reference surface 650 r having the singlecurvature may be a portion of the convex surface 350 b of FIG. 2A.Further, a distance between each point on the first section 650 b(n-k−1), the second section 650 b (n-k), and the third section 650 b(n-k+1) and the virtual reference surface 650 r may not exceed 10 μm, orpreferably, about 5 μm.

The concave part 650 a of the upper surface 650 may also include theplurality of sections 650 a 1 to 650 an and these sections 650 a 1 to650 an may include the first, second, and third sections similar to theexemplary embodiment described above with respect to the convex part 650b. The plurality of sections 650 a 1 to 650 an may be configured by themethod similar to the plurality of sections 650 b 1 to 650 bn, and adetailed description thereof will be omitted to avoid overlappingdescription. However, the thicknesses of the plurality of sections 650 a1 to 650 an, respectively, may be smaller than those of the plurality ofsections 650 b 1 to 650 bn, respectively.

The plurality of sections 650 a 1 to 650 an may be disposed inconsideration of the light directional distributions (see FIG. 19) foreach spectrum of the light emitting element 200 a. Therefore, theplurality of sections 650 a 1 to 650 an are disposed in the areas of 15°or more from the central axis, and the relatively smaller number ofsections 650 a 1 to 650 an may be disposed in the area less than 15°from the central axis.

FIG. 22 is a schematic diagram for describing the color distribution oflight implemented by the lens of FIG. 19.

Referring to FIG. 22, the light emitted through the lens 600 is dividedinto, for example, a dark blue area B and a dark yellow area Y. Sincethe light incident surface 630 and the upper surface 650 have a rotatingbody shape symmetrical to the central axis, each of the areas B and Ymay be represented by a ring shape.

As the light incident surface 630 and the upper surface 650 of the lens600 may be divided into denser sections, the light emitted through thelens 600 may be divided into more areas B and Y.

FIGS. 23A and 23B are simulation diagrams for describing the spatialdistribution of light depending on whether the plurality of sections isformed, in which FIG. 23A illustrate the spatial distribution of lightin the case in which the plurality of sections is not present and FIG.23B illustrate the spatial distribution of light depending on theformation of the plurality of sections.

In order to find out the spatial distribution for each spectrum of thelight emitted through the lens, blue light and green light areidentically incident into an area i of 20° or less from the central axisbased on the light incident surface and an area ii of 30° to 50° fromthe central axis to simulate the color distribution of lighttransmitting the lens.

As illustrated in FIG. 23A, when the plurality of sections is notformed, the light incident into the area i is mixed well, but greenlight of the light incident into the area is not diffused well, and thelight incident into the area ii is intensively distributed into a narrowspace. The concentration phenomenon of green light generates the colordeviation.

Meanwhile, as illustrated in FIG. 23B, when the plurality of sections630 a 1 to 630 an, 650 a 1 to 650 an, and 650 b 1 to 650 bn is formed,it may be appreciated that the light incident into the areas i and ii ismixed well and is widely diffused. Therefore, when light is incidentinto the overall area of the light incident surface, the blue light andgreen light are widely diffused and thus the color mixing may be good.

FIGS. 24A and 24B are photographs illustrating the actually implementedcolor distribution of light, in which FIG. 24B is an enlarged photographof a portion of FIG. 24A. The color distribution of light is obtained byphotographing an image of light irradiated to a diffusion plate spacedby about 25 mm from the lens.

As illustrated in FIGS. 24A and 24B, when the lens according to anexemplary embodiment of the present invention is applied, the dark bluearea B and the dark yellow area Y are repeated in the ring shape by thecolor separation of the blue light emitted from the light emitting diodechip 210 and the yellow light emitted from the wavelength conversionlayer 240.

FIG. 25 is a photograph for describing the color distribution of thelight emitting module in which the plurality of light emitting elementsare each coupled with the lens as described in FIG. 19. The colordistribution of the light emitting module is obtained by photographingthe image of light irradiated to the diffusion plate spaced about 25 mmfrom the lens.

Referring to FIG. 25, it may be confirmed that the light emitted fromthe light emitting module represents uniform color distribution over awide area. That is, the dark blue area B and the dark yellow area Y aredivided into a plurality of dense areas to overlap these areas eachother in the overall light emitting module, thereby implementing uniformcolor distribution.

It will be apparent to those skilled in the art that variousmodifications and variation can be made in the present invention withoutdeparting from the spirit or scope of the invention. Thus, it isintended that the present invention cover the modifications andvariations of this invention provided they come within the scope of theappended claims and their equivalents.

What is claimed is:
 1. A light emitting module, comprising: a circuitboard; light emitting elements disposed on the circuit board, each lightemitting element comprising: light emitting diode chips; and awavelength conversion layer coated on the light emitting diode chips;and a lens disposed on the light emitting elements and configured todiffuse light emitted from the light emitting elements, wherein the lenscomprises a concave part comprising a light incident surface and anupper surface through which the light incident on the lens is emitted,at least one of the light incident surface and the upper surfacecomprises sections disposed at least 15° from a central axis andsequentially connected in a first direction, the sections comprisesequentially connected first, second, and third sections, andthicknesses of the first, second, and third sections are each at least 1μm, and are less than the width of the light emitting element.
 2. Thelight emitting module of claim 1, wherein adjacent sections havedifferent curvatures.
 3. The light emitting module of claim 1, whereinthe thickness of each of the sections is at least 1 μm and is less thanthe width of the light emitting element.
 4. The light emitting module ofclaim 1, wherein the concave part and the upper surface of the lens havea rotating body shape with respect to the central axis.
 5. The lightemitting module of claim 1, wherein: the light emitting diode chipcomprises a flip-chip type light emitting diode chip flip-bonded to thecircuit board; and the light emitting element is disposed directly underthe concave part of the lens along the first direction.
 6. The lightemitting module of claim 1, wherein: the width of an inlet of theconcave part of the lens is greater than the width of the light emittingelement; and the width of the inlet is less than three times the widthof the light emitting element.
 7. The light emitting module of claim 1,wherein a virtual reference surface having a single curvature extendsacross the first, second, and third sections, respectively.
 8. The lightemitting module of claim 1, wherein: the lens further comprises a lowersurface comprising a flat surface enclosing the concave part and aninclined surface enclosing the flat surface; and the lower surface ofthe lens opposing the upper surface is linearly inclined with respect toa planar surface of light emitting elements.
 9. The light emittingmodule of claim 1, wherein: the upper surface comprises a convex parthaving a decreasing width along the first direction extending away fromthe light emitting elements and a concave part having an increasingwidth along the first direction extending away from the light emittingelements; and the concave part is disposed closer to the central axisthan the convex part.
 10. The light emitting module of claim 9, whereinthe concave part comprises a plurality of sections, and the sections ofthe concave part each comprise a thicknesses less than thicknesses ofthe convex part.
 11. A lens configured to diffuse light emitted fromlight emitting elements, the lens comprising: a concave part defining alight incident surface; and an upper surface through which lightincident on the lens is emitted, wherein at least one of the lightincident surface and the upper surface comprises sections disposed atleast 15° from a central axis and sequentially connected in a firstdirection, the sections comprise sequentially connected first, second,and third sections, and thicknesses of the first, second, and thirdsections are each at least 1 μm and are less than the width of the lightemitting element.
 12. The lens of claim 11, wherein adjacent sectionshave different curvatures.
 13. The lens of claim 11, wherein thethicknesses of each of the sections is at least 1 μm and is less thanthe width of the light emitting element.
 14. The lens of claim 11,wherein the lens has a rotating body shape with respect to the centralaxis.
 15. The lens of claim 11, wherein: the light incident surfacecomprises an upper end surface and side surfaces connected from theupper end surface to an inlet of the concave part; the concave partcomprises a shape having a decreasing width along the first directionextending from the inlet to the upper end surface; and the upper endsurface is substantially flat.
 16. The lens of claim 11, furthercomprising a lower surface comprising a flat surface enclosing theconcave part and an inclined surface enclosing the flat surface, whereinthe lower surface of the lens opposing the upper surface is linearlyinclined with respect to a planar surface of light emitting elements.17. The lens of claim 11, wherein a virtual reference surface having asingle curvature extends across the first, second, and third sections,respectively.
 18. The lens of claim 11, wherein the upper surfacecomprises a convex part having a decreasing width along the firstdirection extending away from the light incident surface and a concavepart having an increasing width along the first direction extending awayfrom the light incident surface; and the concave part is disposed closerto the central axis than the convex part.
 19. The lens of claim 18,wherein the concave part comprises sections each having a thickness lessthan the thicknesses of sections comprising the convex part.